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How to Calculate Intracranial Pressure

Moderate to severe head injuries and neurosurgery carry the risk of increased intracranial pressure, which can be a life-threatening condition 1. Intracranial pressure, or ICP, constantly fluctuates similar to your blood pressure or heart rate 1. For medical professionals to calculate ICP, the patient must be in an intensive care unit; the procedure will require catheter insertion through the skull. After a neurosurgeon introduces the catheter, the critical care nurses will monitor and calculate ICP through use of a pressure transducer and data acquisition systems.

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Keep the patient flat on his back with limited stimulation. Any changes in the environment can increase the ICP of a patient with a brain injury; bright lights, nursing interventions and even a blood draw may elevate the ICP measurements.

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Ensure that the transducer is plugged into both the data acquisition system and the catheter. A normal ICP will fluctuate between 1 to 15 mmHg, or millimeters of mercury. Sudden spikes in pressure or consistent elevations must be correlated with a neurological bedside exam to verify physiological changes versus artifact, such as the patient coughing or gagging.

Follow the neurosurgeon's orders for recording the ICP waveform measurements and calculation. Depending on the stability of the patient, the intensive care nurse may be checking measurements as frequently as every five minutes.

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Record the ICP measurements by hand on a scatter plot graph, which will usually have ICP in mmHg vertically and time increments horizontally. Although calculation of the mmHg pressure is completed within the transducer, closely monitoring for changes in the ICP will alert the nurse to possible deterioration in the patient's status.


Sudden, large fluctuations in ICP can sometimes be correlated with changes in the patient's respiration or ventilator settings.